diff options
author | Explorer09 <explorer09@gmail.com> | 2016-08-11 10:49:35 +0800 |
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committer | Explorer09 <explorer09@gmail.com> | 2016-08-11 10:49:35 +0800 |
commit | bf35921abb2ad863b3f49b37c2559600304e451e (patch) | |
tree | aa805f4b034262f515352863a943c87fcc0954bf /StringUtils.c | |
parent | b269eb24b09d48cbbcdbb7a68e122d49cb39d0f1 (diff) |
Optimize Strings_startWith()
Use strncmp() combined with a strlen() will give better performance
than a strstr in worst case. Especially when the match prefix is a
constant and not a variable.
While we are at it, replace the match() function in linux/Battery.c,
which uses a naive algorithm, with a macro that does better job by
utilizing Strings_startWith().
$ gcc --version | head -n 1
gcc (Ubuntu 4.8.4-2ubuntu1~14.04.3) 4.8.4
$ uname -m
x86_64
$ size htop.old htop.new
text data bss dec hex filename
137929 15112 3776 156817 26491 htop.old
137784 15104 3776 156664 263f8 htop.new
Signed-off-by: Kang-Che Sung <explorer09 @ gmail.com>
Diffstat (limited to 'StringUtils.c')
-rw-r--r-- | StringUtils.c | 7 |
1 files changed, 6 insertions, 1 deletions
diff --git a/StringUtils.c b/StringUtils.c index b53f5eea..9547a07e 100644 --- a/StringUtils.c +++ b/StringUtils.c @@ -17,10 +17,15 @@ in the source distribution for its full text. /*{ #include <stdio.h> -#define String_startsWith(s, match) (strstr((s), (match)) == (s)) +#define String_startsWith(s, match) (strncmp((s),(match),strlen(match)) == 0) #define String_contains_i(s1, s2) (strcasestr(s1, s2) != NULL) }*/ +/* + * String_startsWith gives better performance if strlen(match) can be computed + * at compile time (e.g. when they are immutable string literals). :) + */ + char* String_cat(const char* s1, const char* s2) { int l1 = strlen(s1); int l2 = strlen(s2); |